U.S. Pat. No. 4,125,342 discloses a rotating cutting head of a reamer formed with a recess open in a radially outward direction and one circumferential direction relative to the axis of rotation, and a reaming blade retained in the recess between opposite radially extending faces of the head and of a clamping shoe that may be adjusted inward of the recess. Two faces portions of the blade are engaged by the respective faces of the head and shoe in area contact in planes which converge in a radially outward direction at a small acute angle to prevent movement of the blade from an initial radially adjusted position under cutting stress. A differential screw engaging the reamer head and the clamping shoe is employed to retain the insert in the cutter head.